1. Field of the Invention
This invention relates to the production of water-extended polyesteramide resins.
2. Summary of the Prior Art
Water-extended resins are a known class of cellular or porous polymeric compositions. See, for example, the articles by Leitheiser et al in Reinforced Plastics, May, 1968, pp. 260-263 and in SPE Journal, 25, pp. 41-45 (October 1969). In these water-extended resins, minute droplets of water are initially incorporated into a matrix of the resin. Besides substantially reducing material costs, other advantages resulting from the ability to disperse water in resins include reduced flammability, i.e., increased fire retardancy, reduced exothermic curing temperatures, lower product densities, and a porous or foam-like structure which is useful for a variety of purposes. Water-extended resins are useful as materials of construction, including fire walls, moldings and castings, paving and flooring applications, and conduits.
Water-extended resins have been made by the polymerization of water-insoluble vinyl monomers in a water-in-oil (W/O) type emulsion, i.e., an inverted emulsion where water forms the discontinuous or dispersed phase and the vinyl monomer forms the continuous phase or matrix. As described, for example, in U.S. Pat. Nos. 3,255,127, 3,256,219 and 3,442,842, water-extended polyester resins have been made by forming a water-in-oil emulsion of an unsaturated polyester resin and styrene, with or without the use of an auxiliary emulsifier, such as a poly(ethylene oxide) type emulsifier. Without the use of auxiliary emulsifying agents, however, reverse emulsions of relatively low water content are produced. Even when auxiliary poly(ethylene oxide) type emulsifying agents are used, difficulties are encountered in in sufficiently emulsifying the water so that most of the water initially added is lost during the polymerization of the unstable emulsion. As described by Horie et al in Journal of Applied Polymer Science, Vol. 11, pp. 57-71 (1967), copolymerization of unsaturated polyester resin with styrene in water-in-oil type emulsions has been carried out with the use of various basic compounds, having a pK.sub.a above 6, such as triethanolamine, sodium hydroxide or calcium hydroxide, as emulsifiers. However, the use of organic nitrogen-containing emulsifiers such as triethanolamine has been found to be incompatible with room temperature curing systems such as methyl ethyl ketone peroxide and cobalt octoate. When inorganic bases such as sodium hydroxide or calcium hydroxide are used, the resulting water-extended polyester after curing, is softer, thus limiting its utility for those applications where hardness of the cured resin is not important.